<style type="text/css">
    .div1{background:#000080;border:1px solid red;/*解决代码*/height:200px;}
    .div2{background:#800080;border:1px solid red;height:100px;margin-top:10px}
    .left{float:left;width:20%;height:200px;background:#DDD}
    .right{float:right;width:30%;height:80px;background:#DDD}
</style>
<div class="div1">
    <div class="left">Left</div>
    <div class="right">Right</div>
</div>
<div class="div2">
    div2
</div>